Method of sandblasting



March 27, 1956 M. E. FRITZE METHOD OF SANDBLASTING Filed Jan. 5, 1953 IN VEN TOR. MAEV/N 5. 59/725 United States Patent METHOD OF SANDBLASTING Marvin E. Fritze, Seattle, Wash., assignor of one-half to Donald E. Hilliard, Seattle, Wash., and one-half to J. C. Fennelly Company, Inc., a corporation of California Application January 5, 1953, Serial No. 329,516

3 Claims. (Cl. 51-8) Pipe is often rusted, corroded or coated interiorly, and it is a tedious and expensive job to remove the scale, rust and other foreign material which collects upon it, and to recondition the pipe for use. There are sandblasting tools provided for the purpose, but owing to the highly abrasive nature of the sand or like particulate material used in the sandblasting operation, such tools in the forms heretofore devised have quickly worn away. Moreover, being of the general nature of nozzles that of apparent necessity have been directed angularly with respect to the axis along which the sandblast material is delivered (which must coincide roughly with the pipes axis), the blasts sand is delivered at a point only, and consequently either the pipe must be rotated relative to the nozzle, or the nozzle must be rotated relative to the pipe, in order to cover the entire interior area of the pipe. If the nozzle must be rotated relative to the pipe, this must be done in a reasonably accurately controlled fashion, otherwise areas within the pipe will be unevenly sandblasted, but when the jet is rotated mechanically or by hand it must be supported for rotation in bearings which are necessarily located close to the nozzle, within the pipe, and which are inevitably subjected to the abrasive effect of the sandblast material and of the dust created by its use. Such bearings quickly deteriorate, and this manner of operation has been found unsatisfactory. Moreover, such procedure is extremely slow, and as has been said, is likely to be uneven in its results.

If, on the other hand, the pipe must be rotated relative to the jet, this requires handling of the pipe, which is often heavy, and special rigging must be used to support it during the sandblasting operation and to traverse it so that it is sandblasted the whole of its length. This is diflicult, expensive and tedious, and moreover, precludes the possibility of sandblasting the interior of a lot of pipe stacked in the pipe yard, or on racks; each pipe must be individually handled. Because of these difficulties, this procedure has proven unsatisfactory.

It is an object of the present invention to provide a method of sandblasting the interior of pipes, which avoids the difliculties mentioned, and which enables the cleansing of the interior of pipes evenly, accurately, thoroughly, and yet quickly and cheaply.

The accompanying drawing illustrates the method and shows a tool capable of performing said method.

In the accompanying drawings, a pipe is shown in axial section in process of being sandblasted, the sandblasting tool being shown in side elevation, but with parts broken away.

The pipe which is in process of being cleaned is indicated in the drawing at P. This pipe is illustrated as having been cleaned at the left hand end, and only a portion at the right hand end still has an incrustation of scale, as indicated at S. The sense of movement of the sandblasting tool is indicated by the arrow A.

The tool consists of a nozzle 1, to which sand is conveyed by air under pressure through a suitable hose of indeterminate length coupled to the nozzle at 11. The

2,739,424 Patented Mar. 27, 1956 nozzle 1 is removably mounted in the coupling 11. It is of extremely hard, abrasion-resisting material, as, for example, tungsten carbide, and it is wholly straight, and is disposed coaxially with the hose and the pipe and directed axially along the pipe P, by means which will be described shortly. material, but not to change its direction.

Spaced a suitable distance beyond the end of the nozzle, and in axial alignment with it, is a deflector 2. This deflector is of generally conical shape, with its vertex 20 nearest the exit of the nozzle 1, but spaced perhaps six inches from the latter, this having been found an effective distance. The surface of the deflector 2 is preferably formed along a curve, as is indicated at 21, so that tangents to this curve at successive points from the vertex towards the base 22, and lying in a radial plane, are successively less steep with relation to the axis of the conical deflector 2. Preferably, but not necessarily, the curve 21 is formed as the arc of a circle struck from a point such as C, located on a line which is at 45 to the axis of the cone, and outwardly of a projection of the margin of the cones base at 22, and likewise outwardly of its vertex at 20.

The functionof this deflector 2 is to change the direction of the blast material. It is likewise of very hard material, such as tungsten carbide, already mentioned, but since it has surfaces angularly disposed relative to the direction of the sandblast, and impinged thereby, it will inevitably wear in time, even-more than the nozzle, which has no such angulariy disposed surfaces, and so it is removably mounted in a base mount 3, the two being indicated at 23 as relatively threadedly connected, whereby the deflector 2 may be removed when badly worn and a new one may be supplied to replace it.

It is preferred that the deflector and the ,nozzle be fixedly spaced in use, one from the other (although the spacing might be variable) so that they may be moved conjointly axially of the pipe. To such ends spacers or struts 4 are employed, being preferably in the form of simple bars or straps of metal, these extending from the ring or collar 41 which surrounds and is mounted upon the coupling 11 at the base of the nozzle, to the base mount 3 which supports the deflector 2. Although these spacer bars 4 are disposed edgewise to the blast material as it leaves the deflector 2, they will inevitably wear from the abrasive material, hence they are removably secured in place, as by the bolts 40, and in addition, when wear occurs in the vicinity of the base circle 22 of the deflector the notches so abraded in the spacers 4 may be filled in with hard weld material, and thus they will have a reasonably long life. In any event, they are of simple form and readily replaced.

In order to support the assembly within pipes of varying diameter and to dispose the nozzle and cone with reasonable accuracy axially of the pipe, guide elements such as the bolts 42 are employed, these being threadedly received in the ring or collar 41 and in the base mount 3 respectively. Even though there may be but slight room for adjustment if a pipe of larger diameter is to be cleaned, the shorter guide bolts 42 may be removed and longer ones used to replace them. Thus any given tool may be used within pipes of different diameter.

In use, an assembled tool of this nature, connected to any suitable source of abrasive particulate material, and of air under blast pressure, is introduced into an end of the pipe to be cleaned, and the blast is commenced. The particulate material is blown directly through the nozzle 1, never needing to depart from its axial path, and abrading the nozzle to only a minimum degree, and issues as a concentrated stream, as indicated at 9. The vertex 20 is so positioned as to lie approximately axially within this blast stream 9, and so the curved surface 21 deflects Its function is to confine the blast and diverts the stream 9 substantially equally in all radial directions, and changes. it into a generally fiat conical sheet of particles, as indicated at 91, spreading quite evenly in all radial directions'at once from the base of the deflector. No rotativeparts are neededa tangent to the curve 21 at the base circle 22 would be slanted with relation to the cones axis, by reason of the location of its center of curvature as already described, and because the conical blast sheet 9E leaves the deflector at such a tangent, this sheet of particulate material is not directed outwardly perpendicularly to the axis, but rather is inclined with respect to the axis. This is important in that the material after striking the wall of the pipe does not tend to pile up back of the conical sheet 91-, but rather is forced ahead of this sheet, as is indicated at 9-2. Also, because of the axial direction of discharge of the blast from the nozzle, as distinguished from a lateral discharge, a powerful suction is created through the pipe in the same sense asthe blast discharge, which likewise tends to sweep sand and loosened rust, etc., out at the distant (right hand) end of the pipe.

Now it will be clear that by thus discharging and deflecting the particulate mass, and by shifting the tool and the conical sheet of particles axially within the pipe as, for example, in the sense of the arrow A, thescale S iscleaned simultaneously from the interior wall of the pipe and all around the 360 extent of these Walls, and is similarly cleaned and forced ahead progressively as the tool is shifted axially. If the shifting is accomplished at a substantially constant rate, as is preferred, and as can be done by an experienced operator, the cleansing is quite uniform. It has been found that a single pass at a speed which is generally related to the quantity of particles and the area of the pipe wall.-that is to say which is reasonably related to the number of particles striking within a given unit area in a given unit timewill elfect quite satisfactory cleansing. However, the normal procedure is to pass the tool once through the pipe in one direction, to remove most of the incrustation, and then to withdraw it in the reverse direction, to polish the pipe and to remove any residue, so that in effect the pipe is sandblasted interiorly' with two passes, and thus in a Because.

UNITED STATES PATENTS 434,518 Mertz Aug. 19, 1.890 518,560 Black Apr- 137, 1894 1,427,822 Kennedy et al Sept; 5, 1922v 40 2,089,597 Carter Aug. 10, 193.7

2,303,088 Perkins Nov.. 24,, 1942-;

4 fraction'of the time commonly required the pipe is thoroughly cleaned,.. the abraded and abrading material is, pushed ahead out the distant end of the pipe, and the entire operation can be accomplished without any handling of any length of pipe. Indeed, it is possible to clean an entire stack of pipes without disturbing the stack.

While the operation isdi'sclosed above as a sandblasting operation, and that. will constitute the. usual practice, it will be clear that the particles may be larger, and the operation will then become. a shot-peening. operation. The tool and method: are well suited. to such a. modification. I It is intended to include such an operation within the term sandblasting, as used herein.

I claim as my invention:

1. A method of sandblasting the interior of a pipe or the like, which comprises directing a.- stream of particulate material generally axially within the pipe, deflecting such stream radially in all directions at once in the general form of, a. conical sheet. of particles against the: walls of the pipe, and. shifting the deflected cone of particles axially along the. pipe.

2. A. method of sandblasting the: interior of a pipe or the like, as defined in claim 6, wherein the deflected cone of. particles is; shifted at a substantially constant rate axially, offthe pipe.

3. A method of sandblasting the interior of a pipe or the; like, which; comprises delivering a sheet of particulate material in conical form, and generally coinciding axially with the, pipes axis,.at high velocity, to: impinge the pipes.

interior wall about; a circle, and efiecting. relative movement between such. sheet of material and the pipe, axially of the pipe,.to sweep the. entire interior of the pipe.

References Cited in the file of this patent 

